The present invention relates to a device for quenching an electric arc, usually provided on a switching apparatus of an electrically operated device.
Conventional arc quenching devices, such as magnetic arc quenching arrangements or devices for generating quencher gases or devices operated with the aid of compressors and storage containers have been usually very expensive and required a great deal of space.
The purpose of arc quenching devices is to quench an electric arc which occurs in switches upon switching them off or breaking a circuit. Such electric arcs often occur during the opening of contacts due to steaming of the last metallic bridges, caused by joulean heat. In circuit breakers and power control switches such arcs must be extinguished as fast as possible, and a sufficient insulation must be established between the contacts. If in the case of direct current flowing through the circuit of the switch a great arc voltage should be reached in the switching chambers, in the case of alternating current an effective load carrier between a zero current and a recovery voltage must be obtained in a short time. This substantially depends on the type of the switch and on whether an ultimate current interruption takes place in one or a number of zero passages. It is, however, important that an electric arc be sufficiently cooled down.
Various means have been utilized for quenching arc between two normally open contacts. It has been known that in order to quench switch arcs magnetic fields in switching chambers have been used and cooling down has been obtained on respectively designed arc-resistant walls of the chambers.
Circuit breakers for average voltage which operate in accordance with the above described method have required comparatively large quenching chambers and have been therefore rather expensive.
Switches operated with medium and high voltage devices have been used, in which an intensive gas stream is generated to cool the zone where the arc occurs. With this method it can be provided that the quenching gas stream would be produced by the switch itself. A switch which operates in accordance with such principle is disclosed in EP-OS 0,068,951. In other conventional devices the quenching gas is brought to a required pressure by means of compressors and stored in containers. However, both means for arc quenching are considerably expensive.